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278                                ALASKAN GLACIER STUDIES
of a half mile, and even shallower near the glacier, which has therefore been able to plough up the mud of the sea bottom into the new terminal moraine that rose above the bay in 1910. In this eastern half, therefore, no icebergs were discharged, as was the case in 1909, and a few streams flowed into the bay across the mud moraine. Only on the extreme eastern edge of this ice cliff was the new terminal moraine made up of anything but mud. There the beach gravels were being pushed up into a ridge 200 feet long, 180 feet wide and 20 feet high, and filled with mussel and other shells, with barnacles attached to pebbles, and with seaweed. In front of this push moraine were three folds of the compact clay, forming ridges parallel to the front of the moraine against which the ice was advancing. The one nearest the push moraine was breached axially at the crest.
Between July 2 and September 6, 1910, there was sufficient advance along this margin of the glacier to dam back a portion of the tide flats of early summer into a small lake.
The Lobate Eastern Margin. The eastern margin of Columbia Glacier is a sinuous lobate terminus ending on high and low land of the alternating rock hills and plains. Along this eastern margin Gilbert described phenomena in 1899 similar to those which he observed on Heather Island. "There was an inner push moraine, chiefly or wholly of drift and running parallel to the ice margin. There was an outer push moraine, less regular in its distance and associated with disturbance of the forest and the meadow peat. In the tract between the two many prostrate trunks were seen, showing that in places the front of the forest had been crowded back several hundred feet. Many of the trees that were overturned but not overridden, retained their bark, branches, and even minor twigs, but the leaves had fallen. On disturbed forest soil Coville found three young spruces which had grown since the catastrophe. In each case the age, as shown by rings of growth, was seven years. The date of the ice maximum was therefore not later than 1892 and may have been that year."
We do not know the behavior of this margin during the earlier oscillations described for the Heather Island and western termini. Advance had taken place here before June, 1909, however, for Grant states that "on the eastern edge of the glacier there was a zone of perhaps 200 feet between the maximum advance in recent years into the forest and the front of the ice." l
On August 24, 1909, the National Geographic Society's expedition was able to compare the exact conditions along the lobate margin with those ten years before. We climbed the spur east of the glacier to Gilbert's plane table and photograph station (Sta, I), at an elevation of 1497 feet; and we also walked some distance along the marginal stream and lake southeast of the glacier, but did not walk over any of the glacier edge itself.
On comparing the photographs from this spur taken by Gilbert on June 26, 1899,* with the conditions on August 24,1909, we found the following changes. At the margin of the eastern ice cliff there was an advance southwestward into the bay which we estimate to be between 1000 and 1500 feet. There was a broadening of the glacier by several hundred feet, as also shown by Grant's observation in June, 1909, but in August the ice margin had as yet not extended to the maximum of 1892. In places, however, it was within a short distance of the forest.
1 Personal communication.
 Reproduced as Plate IX, Harriman Alaska Expedition, Vol. El, 1904,